> at the 10K foot level the model was the same - input loop, window messages, and window procs.

That's a fairly broad description, isn't it? At least I have a hard time coming up with windowing API models that don't fundamentally work that way at the lower levels. (About the only exception think of is a text-based library that shipped with Microsoft BASIC 7.0, and that was mainly because the language didn't support any of the abstractions needed for callbacks.)